Method and apparatus for use in an inductive sensor coin selector

ABSTRACT

A method and apparatus for use in an inductive sensor coin selector in which the acceptability of a coin is dependent upon a function of an examination of the output of an inductor in the absence of coins and an examination of the output of the inductor in the presence of the coin.

United States Patent [1 1 Heiman et a1.

[' Nov. 11, 1975 METHOD AND APPARATUS FOR USE IN AN INDUCTIVE SENSORCOIN SELECTOR [75] Inventors: Fred P. Heiman, Delran, N.J.;

Gerhard Herzog, Lugano,

Switzerland [73] Assignee: Mars, Inc., McLean, Va.

[22] Filed: Oct. 12, 1973 21 App]. No.: 405,926

[30] Foreign Application Priority Data Oct. 12, 1972 United Kingdom47164/72 [52] US. Cl. 194/100 A; 194/1 K [51] Int. Cl. G07F 3/02 [58]Field of Search 209/1116, 81 R, 81 A; 73/163; 194/97 R, 100 R, 100 A, lK, DIG.

[56] References Cited UNITED STATES PATENTS 2,690,258 9/1954 Cox209/1116 2,982,389 5/1961 Dietrich 194/97 R 3,561,580 2/1971 Meloni194/100 A 3,741,363 6/1973 Hinterstocker 194/100 A 3,797,307 3/1974Johnston 194/100 A X Primary Eruminer-Robert B. Reeves AssistantExm11iner.1oseph J. Rolla Attorney, Agent, or Firm-Davis, Hoxie,Faithful] & Hapgood ABSTRACT A method and apparatus for use in aninductive sensor coin selector in which the acceptability of a coin isdependent upon a function of an examination of the output of an inductorin the absence of coins and an examination of the output of the inductorin the presence of the coin.

27 Claims, 4 Drawing Figures METHOD AND APPARATUSFOR use IN AN INDUCTIVESENSOR COIN SELECTOR We have found in discriminating betweencoinsftokens and the like in a coin selector by means of an inductivesensor that practical improvement in discrimination can be achieved byproducing a function dependent upon both the information produced by thesensor in the presence of the coin and the information produced by thesensor at a slightly earlier or later time when no coin is in thepresence of the sensor, and then comparing the value of this functionwith values for acceptable coins.

According to the method of our invention, the coin or other object to betested is caused to pass along a known path past one or more poles of aninductor on the one side of the path. The method further comprises thesteps of examining a characteristic of the inductor output signal in theabsence of coins from the presence of the sensor, examining the samecharacteristic with a coin in the presence of the sensorfproducing asignal which is a function of these two examinations, and pro ducingasignal indicative of the acceptability of the coin tested. As a furtherdevelopment in our method, at the point where the coin is caused to passthe inductor on one side of the path, the coin is caused to pass betweenthat inductor and an electrically conductive target on the other side ofthe path.

The method of our invention tends to minimize errors resulting fromshifts in value ofthe'reference standards upon which the coinexamination depends, such as oscillator idling frequency, the durationof pulse counting periods and the like. The method employing the step ofpassing the coin between the sensor and a target is particularly usefulin minimizing errors caused by variations in the physical position ofthe sensor relative to the passageway, as in apparatus, where the sensor is mounted on a moveable passageway sidewall. Our invention alsocomprises the combination of ele ments of a coin selector apparatus asdescribed below.

In the drawings:

FIGS. 1 and 2 show a front schematic and a side schematic view (cutawayalong line 2-2 of FIG. 1) of a portion of a coin selector apparatusaccording to our invention.

FIG. 3 is a block diagram of an embodiment of our invention.

FIG. 4 is a block diaagram of another embodiment of our invention.

The figures are intended to be representational and are not necessarilydrawn to scale.

Throughout this specification the term coin is intended to mean genuinecoins, tokens, counterfeit coins, slugs, washers, and any other itemwhich may be used by persons in an attempt to use coinoperated devices.

In the apparatus of FIG. 2, an inductor having one or more pole pieces22 is located on one side of a coin passageway 30. The passageway isdefined by two Opposite the inductor 20 embedded in or on the innersurface of the sidewall 32, on the other side of the passageway 30 fromthe inductor 20, is a conductive target 40 such as a thin disc of copperor other highly conductive material. In the absence of coins and otherobjects from the vicinity of the inductor 20 in the passageway 30, thesignal across the inductor terminals is affected by the presence oftarget 40. If sidewall 34 varies in position with respect to sidewall32, that signal will vary as a function of the relative locations of theinductor 20 and the target 40. Details regarding the choice of asuitable inductor 20 and a circuit in which such an inductor may be usedmay be found in British specifications 16538/71 and 8385/72, and US.Ser. No. 405,881, filed Oct. 12, 1973, now US. Pat. No. 3,870,137 whichis a continuation of US. Ser. No. 255,814, filed May 22, 1972 assignedto the assignee of this patent, now abandoned.

In FIG. 3, the inductor 320 is connected to an examining station circuit350 in such a manner that the output of the station 350 is a function ofmaterial in the field of the inductor 320. When a target 340 is locatedacross the passageway 330 from the inductor 320, the output of thestation 350 is modified in an amount dependent upon the relativepositions of the sidewalls 332 and 334. The target 340 need not beincluded in the apsidewalls 32 and 34, and a coin track 36 attached to"sidewall 34. Sidewall 32 is fixed to the rest of the coin discriminatorapparatus and sidewall 34, on which in paratus if dependence uponrelative sidewall positions is not desired. The output of the station350 is applied to both switching means 362 and 364, as is a sequence oftime pulses from time pulse generator 360. When a coin examination is inprogress, and at all other times except when the 0 output of monostable361 is produ c ing a pulse, switching means 362 is enabled by the Qoutput of monostable 361; causing the output of station 350 to bedirected to register 37] for the duration of the time pulse. Functioncircuit 385 produces a value which is a function of the test value whichis stored in the register 371 and of the reference value which wasstored in the register 370 as :representative of the output of station350 when nocoin was present in the apparatus. That signal from thefunction circuit 383, which may for example be the arithmetic differencebetween counts stored in registers 370 and 371, is transmitted to thecomparison-and. memory circuit 390. The comparison and memory circuit390 contains information regarding values forfvalid coins and means forcomparing such values with the values received from the function circuit383. If the comparison and memory circuit 390 determines that such areceived value is within the range for an acceptable coin, it produces asignal indicative of the fact that the coin being tested has passed theparticular test. Further information about comparison and memorycircuits suitable for use according to this invention may be found in anapplication Ser. No. 405,927 filed Oct. 12, 1973 and assigned to theassignee of this patent.

The reference value stored in register 370 is entered in the same manneras a test value is entered into register 371. The reference value isentered into register 370 at three different times under control of thehouse keeping circuit 365, OR gate 366, AND gate 367 and monostable 361.The housekeeping circuit 365 produces signals which are transmitted viathe OR gate 366 and the AND gate 367 to trigger the monostable 361 asfollows: when power is first applied to the coin selector each time asignal is received that the machine associated with the coin selectorhas been instructed to vend, and every one second. AND gate 367,however, receives a signal for the duration of the period from when thecoin selector first senses the presence of a coin (arrival) to thedeparture of the coin, which inhibits the flow of triggering signalsduring that period. As a result, the reference value stored in register370 will not include values influenced by the presence of a coin in thevicinity of a sensor. In a variation of this embodiment which ispresently preferred, the reference value is stored when the housekeepingcircuit 365 produces signals either approximately 300 milliseconds afterpower is first applied to the coin selector or approximately 300milliseconds after an acceptable signal with respect to any denominationis received from a portion of the coin selector not dependent upon thereference value (e.g. a low frequency examination), followedby theabsence of a coin accept signal (i.e.: a high frequency reject). Thedelay, which may be produced by the use of a counter within thehousekeeping circuitry 365 to count pulses from the time pulse generator360, assures a sharp, relatively noise-free pulse from the monostable361 and, in the second case, assures that the coin leaves the sytembefore the new reference value is entered. As a result, the referencevalue stored in register 370 will not include values influenced by thepresence of a coin in the vicinity of a sensor.

In the event that a linear correction such as the one described abovedoes not provide a satisfactory correction, for example, for variationsin oscillator frequency due to variations in the relative position ofthe sidewall 334 with respect to sidewall 332 or other perturbations ofthe system, the value stored in the register 371 can 1 be modified by adifferent mathematical function dependent upon the count stored in theregister 370.

In one form of this embodiment implemented entirely with digitalcircuitry, the presence of conductive objects in the field of theinductor 320 causes a shift in the frequency of an oscillator comprisingthe station 350. Such an oscillator circuit is discussed in US. Pat. No.3,870,137. The oscillator frequency is measured by use of preciseduration time pulses from the time pulse generator 360 to gate pulses todigital counters comprising the registers 370 and 371. AND gates areemployed for the switching means 362 and 364. The reference pulse whichis stored is the difference (f-fo) between the peak frequency in thepresence ofa coin and the frequency in the absence of coinsf I Inanother form of this embodiment, analog circuits can be used to performat least some of the functions. For example, when the output of a coinexamining station 350 which is indicative of the coin characteristicment of the present invention. The inductor 420 and oscillator 450 andcoin passageway details (not shown) may correspond to those of theembodiment of FlG.'3.

A timing pulse generating means 460 drivesa flipflop f FIG. 4 is a blockdiagram of a digital circuit embodr 461 with a precision duration pulsevia AND gate 463.

the end of each precision pulse period.

In the initial idling frequency monitoring mode of operation theflipflop 461 directs the output of the oscillator alternately to counter470 or counter 47] for the precision pulse period, for example 1millisecond. AND gates 462 and 464 are employed to switch the oscillatoroutput between the counters and AND gates 466 and 468 are used to definethe duration of the counting periods.

When no coin is in the vicinity of the inductor 420, one of the counters470 and 471 stores a value representative of the output frequency of theoscillator 450, while the other is measuring the oscillator outputsignal. When the coin selector apparatus detects the arrival of a coinwithin the apparatus by arrival/departure detecting means 455, thedetails of which are not a part of this invention, an arrival signal isdirected to AND gate 463 to inhibit that gate and stop the alternationbetween counters of the oscillator output signal. Instead, one of thecounters 470 or 471 remains connected to receive and count theoscillator output signal for the precision pulse period, while the othercontinues to store the last count value, stored prior to the arrivalsignal. This stored value is representative of the idling frequency ofthe oscillator 450 just prior to the coinexamination which is to follow.Alternatively, the idling frequency can be determined in the mannerdescribed for the apparatus of FIG. 3.

When the coin enters the field of the inductor, the oscillator frequencyincreases. During each subsequent precision pulse period, the comparisonmeans 473 sets the flipflop 485 as soon as the pulse count of thefrequency increases above the pulse count stored as representative ofthe idling frequency, and thereby activates AND gate 489. All of theremaining pulses from the oscillator 450 during that period aretransmitted via OR gate 487 and AND gate 489 to the memory system 490for comparison with information stored there regarding acceptable coins.

Following the end of each precision pulse period, during a briefinterlude prior to the start of the next precision pulse period, a resetpulse is produced on lead 479 from the pulse generating means 460. Itresets flipflop 485 and appropriate elements in the memory system 490.The reset pulse is also applied to gates 476 and 478, one of which isenabled by a signal from the flipflop 461 which controls which of thecounters 470 or 471 is to count in the next period, causing only thatcounter to be reset.

When the coin departs from the coin selector apparatus, the arrivalsignal from the arrival/departure sensing means 455 ceases, AND gate 463is no longer inhibited, and the apparatus returns to the idlingfrequency monitoring mode of operation.

We claim:

1. A method for examining coins with respect to authenticity includingthe steps of producing an alternating magnetic field,

subjecting a coin to the field,

producing a first signal having a quality representative of the degreeof interaction of the coin with the field,

determining a first value of said quality at a time when no coin is inthe presence of the field, determining a second value of said quality atanother time when the coin is in the presence of the field,

producing a second signal having a value representative of a functionwhich is dependentupon both the first value and the second value, and Icomparing the value representative of the function for the coin with avalue representative of the function for an acceptable coin.

2. The method of claim 1 wherein the value representative of thefunction is the arithmetic difference between the first and secondvalues.

3. A method for examining coins with respect to authenticity includingthe steps of producing an alternating magnetic field,

subjecting a coin to the field,

producing a first signal having a quality representative of the degreeofinteraction of the coin with the field.

determining a first value of said quality at a time when no coin is inthe presence of the field,

determining a second value of said quality at another time when the coinis in the presence of the field storing one of the values,

producing a second signal having a value representative of a functionwhich is dependent upon both the first value and the second value, and

comparing the value representative of the function for the coin with avalue representative of the function for an acceptable coin.

4. The method of claim 3 wherein the value representative of thefunction is the arithmetic difference be tween the first and secondvalues.

5. The method of claim 4 wherein the quality representative of thedegree of interaction is the frequency of the magnetic field.

6. The method of claim 5 wherein the first and second values of thequality are each produced by counting the pulses of the field frequency,further including the step of storing one of said values for use inproducing the second signal.

7. The method of claim 6 wherein values representative of the functionfor the coin are produced throughout the period during which the coin issubjected to the field further including the step of determining whetherthe coin is acceptable only if the largest of said values is withinpredetermined limits for acceptable coins of a given denomination.

8. The method of claim 7 wherein the value representative of thefunction is the arithmetic difference between the first and secondvalues.

9. The method of claim 3 wherein the quality representative of thedegree of interaction is the frequency of the magnetic field.

10. The method of claim 9 wherein the first and second values of thequality are each produced by counting the pulses of the field frequency,further including the step of storing one of said values for use inproducing the second signal.

11. The method of claim 10 wherein values representative of the functionfor the coin are produced throughout the period during which the coin issub jected to the field further including the step of determiningwhether the coin is acceptable only if the largest of said values iswithin predetermined limits for acceptable coins of a givendenomination.

12. The method of claim 11 wherein the value repre sentative of thefunction is the arithmetic difference between the first and secondvalues.

l3. The method of claim 3 wherein values represen tative of the functionfor the coin are produced throughout the period during which the coin'issubjected to the field further including the step of determiningwhetherthe coin is acceptable only if the largest of said values is withinpredetefmiried limits for acceptable coins of a given denomination.

14. Apparatus for examining coins with respect to authenticity includingi v inductor means for subjectinga coin to an alternating magneticfield, i i i means for producing a first signal having a quality.representative of the degree of interaction of the coin with the field,

means for storing a first value of the quality of the first signaldetermined when no coin is in the presence of the field,

function generator means connected to receive the first value and asecond value of the first signal de' termined when the coin is in thepresence of the field to produce a function of the first and secondvalues, and

comparator means connected to receive the output of the functiongenerator means for comparing a value representative of the function ofthe coin with a value representative of the function of an acceptablecoin.

15. The apparatus of claim 14 further including a coin passageway havingnon-conductive sidewalls between which coins to be examined pass along apredetermined path and a conductive target, wherein the inductor islocated on one side of the path and the target is located on the otherside of the path opposite the inductor.

16. The apparatus of claim 15 wherein the first signal producing meansis an oscillator having the inductor as a frequency determiningcomponent.

17. The apparatus of claim 15 wherein the quality of the degreeofinteraction of the coin with the field is the frequency of the firstsignal.

18. The apparatus of claim 15 wherein the function generator meansproduces the arithmetic difference between the first and second values.

19. The apparatus of claim 14 further including a coin track along whichcoins to be examined are conducted through the field, a firstnon-conductive sidewall on one side of the track to which the inductoris mounted, a second non-conductive sidewall on the other side of thetrack to which a conductive target is mounted opposite the inductor, thesidewalls being relatively moveable.

20. The apparatus of claim. 19 wherein the first signal producing meansis an oscillator having the inductor as a frequency determiningcomponent.

21. The apparatus of claim 19 wherein the quality of the degree ofinteraction of the coin with the field is the frequency of the firstsignal.

22. The apparatus of claim 19 wherein the function generator meansproduces the arithmetic difference between the first and second values.

23. The apparatus of claim 14 wherein the first signal producing meansis an oscillator having the inductor as a frequency determiningcomponent. i

24. The apparatus of claim 14 wherein the quality of the degreeofinteraction of the coin with the field is the frequency of the firstsignal.

25. The apparatus of claim 14 wherein the function generator meansproduces the arithmetic difference between the first and second values.

' 26. Apparatus for examining coins with respect to authenticityincluding a coin passageway along which a coin to be examined will passon a predetermined path,

an oscillator including an inductor within its frequency determiningcircuit which produces a first signal having a frequencyrepresentativeof the degree of interaction of the magnetic field of the inductor withcoins within the field,

means for preserving a first value of the frequency of the first signaldetermined when no coin is in the UNITED STATES PATENT AND TRADEMARKOFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,918,564 DATED November 11,1975 INVENTOR( 1 Fred P. Heiman and Gerhard Herzog It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Col

[SEAL] 1, line 49, "diaagram" should be -diagram.

2, line 36 "385" should be "383",

5, (claim 3) line 21, there should be a comma after "field'h 5, line 22should not be indented.

Signed and Scaled this Twentieth Day of July 1976 A ttes t:

RUTH C. MASON Arresting Officer C.MARSHA LL DANN Commissioner uj'Parenrsand Trademarks

1. A method for examining coins with respect to authenticity includingthe steps of producing an alternating magnetic field, subjecting a cointo the field, producing a first signal having a quality representativeof the degree of interaction of the coin with the field, determining afirst value of said quality at a time when no coin is in the presence ofthe field, determining a second value of said quality at another timewhen the coin is in the presence of the field, producing a second signalhaving a value representative of a function which is dependent upon boththe first value and the second value, and comparing the valuerepresentative of the function for the coin with a value representativeof the function for an acceptable coin.
 2. The method of claim 1 whereinthe value representative of the function is the arithmetic differencebetween the first and second values.
 3. A method for examining coinswith respect to authenticity including the steps of producing analternating magnetic field, subjecting a coin to the field, producing afirst signal having a quality representative of the degree ofinteraction of the coin with the field. determining a first value ofsaid quality at a time when no coin is in the presence of the field,determining a second value of said quality at another time when the coinis in the presence of the field storing one of the values, producing asecond signal having a value representative of a function which isdependent upon both the first value and the second value, and comparingthe value representative of the function for the coin with a valuerepresentative of the function for an acceptable coin.
 4. The method ofclaim 3 wherein the value representative of the function is thearithmetic diFference between the first and second values.
 5. The methodof claim 4 wherein the quality representative of the degree ofinteraction is the frequency of the magnetic field.
 6. The method ofclaim 5 wherein the first and second values of the quality are eachproduced by counting the pulses of the field frequency, furtherincluding the step of storing one of said values for use in producingthe second signal.
 7. The method of claim 6 wherein valuesrepresentative of the function for the coin are produced throughout theperiod during which the coin is subjected to the field further includingthe step of determining whether the coin is acceptable only if thelargest of said values is within predetermined limits for acceptablecoins of a given denomination.
 8. The method of claim 7 wherein thevalue representative of the function is the arithmetic differencebetween the first and second values.
 9. The method of claim 3 whereinthe quality representative of the degree of interaction is the frequencyof the magnetic field.
 10. The method of claim 9 wherein the first andsecond values of the quality are each produced by counting the pulses ofthe field frequency, further including the step of storing one of saidvalues for use in producing the second signal.
 11. The method of claim10 wherein values representative of the function for the coin areproduced throughout the period during which the coin is subjected to thefield further including the step of determining whether the coin isacceptable only if the largest of said values is within predeterminedlimits for acceptable coins of a given denomination.
 12. The method ofclaim 11 wherein the value representative of the function is thearithmetic difference between the first and second values.
 13. Themethod of claim 3 wherein values representative of the function for thecoin are produced throughout the period during which the coin issubjected to the field further including the step of determining whetherthe coin is acceptable only if the largest of said values is withinpredetermined limits for acceptable coins of a given denomination. 14.Apparatus for examining coins with respect to authenticity includinginductor means for subjecting a coin to an alternating magnetic field,means for producing a first signal having a quality representative ofthe degree of interaction of the coin with the field, means for storinga first value of the quality of the first signal determined when no coinis in the presence of the field, function generator means connected toreceive the first value and a second value of the first signaldetermined when the coin is in the presence of the field to produce afunction of the first and second values, and comparator means connectedto receive the output of the function generator means for comparing avalue representative of the function of the coin with a valuerepresentative of the function of an acceptable coin.
 15. The apparatusof claim 14 further including a coin passageway having non-conductivesidewalls between which coins to be examined pass along a predeterminedpath and a conductive target, wherein the inductor is located on oneside of the path and the target is located on the other side of the pathopposite the inductor.
 16. The apparatus of claim 15 wherein the firstsignal producing means is an oscillator having the inductor as afrequency determining component.
 17. The apparatus of claim 15 whereinthe quality of the degree of interaction of the coin with the field isthe frequency of the first signal.
 18. The apparatus of claim 15 whereinthe function generator means produces the arithmetic difference betweenthe first and second values.
 19. The apparatus of claim 14 furtherincluding a coin track along which coins to be examined are conductedthrough the field, a first non-conductive sidewall on one side of thetrack to which the inductor is mounted, a second non-conductive sidewallon the other side of the track to which a conductive target is mountedopposite the inductor, the sidewalls being relatively moveable.
 20. Theapparatus of claim 19 wherein the first signal producing means is anoscillator having the inductor as a frequency determining component. 21.The apparatus of claim 19 wherein the quality of the degree ofinteraction of the coin with the field is the frequency of the firstsignal.
 22. The apparatus of claim 19 wherein the function generatormeans produces the arithmetic difference between the first and secondvalues.
 23. The apparatus of claim 14 wherein the first signal producingmeans is an oscillator having the inductor as a frequency determiningcomponent.
 24. The apparatus of claim 14 wherein the quality of thedegree of interaction of the coin with the field is the frequency of thefirst signal.
 25. The apparatus of claim 14 wherein the functiongenerator means produces the arithmetic difference between the first andsecond values.
 26. Apparatus for examining coins with respect toauthenticity including a coin passageway along which a coin to beexamined will pass on a predetermined path, an oscillator including aninductor within its frequency determining circuit which produces a firstsignal having a frequency representative of the degree of interaction ofthe magnetic field of the inductor with coins within the field, meansfor preserving a first value of the frequency of the first signaldetermined when no coin is in the field, function generator means forproducing second signal having a value representative of the differencebetween the first value of the first signal and a second value of thefrequency of the first signal determined when the coin is in the field,and a comparator arranged to compare the value of the second signalrepresentative of the difference for the coin with a valuerepresentative of the difference for an acceptable coin.
 27. Theapparatus of claim 26 further including a conductive target located onthe opposite side of the path from the inductor.